Deoxyribonucleic acid, or DNA, is the molecule of life.
It is a large, complex molecule that contains coded genetic information that specifies how every part of our body works. DNA is found in most cells of the body, including white blood cells, sperm cells, hair roots, skin cells, and body tissue. Traces of DNA can also be detected in body fluids such as saliva and sweat.
The DNA molecule is very large compared to other molecules, and is comprised of millions of molecular building blocks, known as base pairs, strung together on a sugar phosphate backbone. This forms the familiar twisted ladder shape of DNA, a structure that is technically known as a right-handed double helix.
The genetic information contained in DNA is coded into the molecule by the arrangement of four different bases that run along the sugar phosphate backbone. These bases are collectively called deoxyribonucleotides and are individually named adenine, guanine, thymine and cytosine (normally abbreviated as A,G,T and C).
Two backbone chains, running in opposite directions, are paired together by the interaction of the four bases. A bonds to T and G bonds with C. It is this specific base-to-base bonding that allows the genetic information contained in DNA to be accurately copied from one generation of cells to the next, and ultimately down family lines from parent to child.
The copying of DNA in the cell is achieved by the two complementary DNA strands splitting apart. This provides access to each side of the chain and allows the strands to be copied by the addition of new bases that bond to the exposed bases on each strand. The new bases join together to form a new strand of DNA, and in this way one double stranded DNA molecule can be pulled apart and copied, and result in two new molecules identical to the first.
The ability of DNA to repair and replicate itself, as well as being the fundamental mechanism of life, is the basis of modern forensic DNA profiling techniques.